1. Field of the Invention
This invention relates to a cable reel which may be used with a cradle and a handset, such as a telephone handset or remote control for electronic apparatus, as found for example in various modes of mass transport including aircraft, vessels, rail and road passenger vehicles. Such handsets and cradles may also be used to facilitate audience participation or interaction in theatres, arenas, lecture theatres, libraries and similar locations.
2. Description of the Related Art
It is known to provide a cradle in the armrest of a chair, such as a seat in an aircraft, for housing a handset comprising, for example, a telephone and/or a remote controller for in-flight entertainment apparatus. Such handsets can also include call functions for the in-flight staff. A typical example is the model RU-AA6501-01 of Matsushita Electrical Industrial Company Limited of Osaka, Japan. Similar handsets and cradles may also be mounted in other locations such as in or on aircraft bulkheads or seat backs: see for example U.S. Pat. Nos. 5,128,993, 5,410,597 and 5,155,766.
Conventionally such cradles comprise a recess in which the handset is stowed and from which the handset can be removed for example by lifting. The handset is electrically powered and connected via a cable which is housed in and may be drawn from a cable reel as the handset is removed from the cradle. As the handset is stowed, the cable is rewound into the reel under spring action, so as to leave no potentially hazardous freely exposed cable loop. To simplify cradle installation as well as helping to ensure proper retraction of the cable, the reel may be housed in or mounted on the cradle, with the cable routed directly from the reel into the recess. Alternatively the cable reel may be mounted separately from the cradle with a cable run or guide extending therebetween (see for example U.S. Pat. No. 5,109,412 and International patent publication no. WO 95/29552).
The cable or reel is often provided with a releasable ratchet mechanism to relieve the spring tension on the extended cable and prevent this tension from being experienced by the user. A known handset cradle incorporating a ratchet mechanism of this kind is illustrated in FIGS. 1-5.
FIG. 1 is an upside down exploded view of a cradle 10 for a telephone handset. A handset cable 14 extends from a handset stowage recess 18 into a spool chamber 16 through a cable exit opening 12. The cable 14 is wound onto or pulled from a spool 20 housed in the chamber 16. The spool 20 is rotatably mounted on a fixed hollow spindle 22. A bifurcated end of the spindle 22 is snap fitted into a pair of D slots 24 formed in the bottom of spool chamber 16. A ribbon cable 26 extends through the spindle 22 into a space within the hub of the spool 20. A portion of the ribbon cable 26 is coiled within this space to form an electrical connection between an exterior multiplug 28 and the rotating end of the handset cable 14 carried by the spool 20.
As shown in FIG. 2, the spool 20 has a spring accommodating recess 30 in one side. A spiral spring 32 has a hooked end 34 engaged in an anchor slot 36 formed in the rim of the recess 30. The other end 38 of the spring 32 is curled to fit within a slot 40 in the bifurcated end 42 of the spindle 22. As the handset cable 14 is paid out, the spool 20 rotates on the spindle 22 and the spring 32 is tensioned. This provides a return bias tending to retract the handset cable 14.
Referring to FIGS. 1 and 3, a lid 44 closes the spool chamber 16. Pins 46, 48, 50, 52, 54, 56 are moulded on the inside of the lid 44 for mounting parts of the ratchet mechanism.
These parts are moulded from a resilient, self-lubricating plastics material such as nylon or acetyl polymer and comprise a ratchet stop/index spring finger 58 secured on pins 46, 48 using Loctite(copyright) 406, a star/ratchet wheel 60 rotatably mounted on pin 50, an oscillating pawl 62 rotatably carried on pin 52 and a centralising spring finger 64 secured on pins 54, 56 in similar manner to stop/index spring finger 58 and pins 46, 48.
The star/ratchet wheel 60 has six raised points 66 alternating with six troughs 68 about its periphery. It also has a raised hub with twelve peripheral ratchet teeth 70, which are engaged by a shoulder 72 on the end of the stop/index finger 58. This allows the star wheel to rotate, anticlockwise as shown, in twelve discrete steps, thereby alternately presenting a point 66 or a trough 68 to the oscillating pawl 62 at each rotational step. The stop/index finger shoulder 72 also retains the wheel 60 on the pin 52. An anti-rotation arm 73 has an end surface that butts up against the points 66 of the star/ratchet wheel to prevent it rotating in the clockwise direction as shown in FIG. 6, but which is deflectable to allow rotation of the star/ratchet wheel 60 in the anticlockwise direction.
FIGS. 4 and 5 show somewhat enlarged views of the top and underside of the oscillating pawl 62 respectively. Centralising spring finger 64 engages in a slot 74 to retain the oscillating pawl 62 on pin 52 and to return it to a rotationally centralised position with some degree of lost motion. An indexing spring arm 76 moulded in one piece with the oscillating pawl 62 engages the ratchet teeth 70 to index the star/ratchet wheel 60 anticlockwise by one step with each clockwise oscillation of the pawl 62. The underside of the oscillating pawl 62 is provided with a projecting stop 78 which interacts with the star/ratchet wheel raised points 66 and troughs 68. In the centralised position of the pawl 62, depending upon the position of the star/ratchet wheel 60, either a point 66 lies immediately in front of the stop 78, thereby preventing rotation of the pawl 62 anticlockwise as viewed in FIG. 3, or the stop lies within a trough 68 which provides sufficient clearance for anticlockwise rotation of the pawl 62 to a limit governed by the centralising spring finger 64. In either position of the star/ratchet wheel 60, the pawl 62 is free to rotate clockwise from the centralised position to a limit controlled by the centralising spring finger 64.
The oscillating pawl 62 carries a tooth 80 positioned to engage a series of teeth 82 upstanding axially from the spool 20 rim (see FIG. 1). Pulling on the handset cable will rotate the spool 20 clockwise relative to the inside of the lid 44 on which the ratchet mechanism is located (or anticlockwise in the spool chamber 66, FIG. 1). This causes the spool teeth 82 to knock against the pawl tooth 80, turning the pawl 62 clockwise in the reference frame of FIG. 3, and indexing the star/ratchet wheel 60 anticlockwise by one step or ratchet tooth 70. Supposing that initially, before pulling on the cable, a point 66 lies immediately in front of the stop 78. The oscillating pawl 62 cannot be rotated anticlockwise away from its centralised position in FIG. 3, which in turn means that the pawl tooth 80 engages one of the spool teeth 82, preventing the spool from rotating anticlockwise relative to the inside of the lid 44, so preventing the cable 14 from rewinding onto the spool under the influence of spring 32. In this condition, pulling on the handset cable 14 will now index a trough 68 into co-operation with the pawl 62, providing clearance for the stop 78. Consequently, releasing the handset cable 14 will now cause it to rewind under the action of spring 32, as the spool teeth 82 can knock aside the cam tooth 80, rotating the oscillating cam 62 anticlockwise in the FIG. 3 reference frame. Pulling and releasing the handset cable 14 yet again will index a point 66 back into co-operation with the stop 78, locking the spool against rewinding. In the result, with each successive pull and release, the handset cable 14 is alternately free for, or locked against, retraction.
Because the spacing of the spool teeth 82 is relatively small (tens, hundreds or even thousands of times less than the cable length) the mechanism enables the cable to be locked against rewinding at a large number of discrete extensions. The number may be sufficiently large that the cable is for practical purposes lockable at any extension.
Inexperienced users of such handsets can find the ratchet mechanism difficult to operate. In particular if, as the handset is being stowed, the cable 14 is momentarily tugged, rewinding of the cable is arrested. This can be confusing. In this situation, users have been known to wind the remaining unretracted cable around the handset and then jam the handset plus unretracted cable into the cradle. Such mistreatment can damage the cable, handset and/or cradle. Alternatively, the user may leave the unwound cable loop dangling, presenting a trip hazard. For this reason, handset cable reels installed in safety critical areas, such as near aircraft cabin gangways, are often not provided with ratchet mechanisms. This ensures that the cable will be correctly rewound after use, but exposes the handset user to inconvenient and uncomfortable cable tension. A more xe2x80x9cuser friendlyxe2x80x9d handset cable reel mechanism is therefore desirable.
GB 1581 487 (Ritter AG) discloses a stowage housing for dental instrument cables and hoses in which the cable or hose is withdrawn from between the windings of a flat coil spring. One or more stops may be fixed to the spring at discrete intervals, for engagement with a fixed pawl, to provide retraction force relief. However, with this arrangement, the number of hose withdrawal lengths at which retraction force relief can be provided is limited.
In accordance with the invention there is provided a handset cable reel mechanism comprising:
a spool;
a handset cable having a length that can be unwound from or rewound onto the spool in use, the spool being resiliently biased to rotate in the cable rewinding direction;
an arresting mechanism selectively engageable to prevent rewinding of the cable and disengageable to allow rewinding of the cable under the spool resilient bias,
wherein such engagement of the arresting mechanism cannot take place over a predetermined portion of the rewinding of the cable length.
Preferably the selective engagement or disengagement of the arresting mechanism is achieved in use by pulling on the cable in the unwinding direction.
Most of the difficulties that arise in the use of handset cable reel mechanisms are due to premature engagement of the arresting mechanism as the user guides the handset during its final approach towards the cradle. A user is more likely to inadvertently tug on the cable as the final portion of its length is rewound. This is particularly so if the cradle is somewhat awkwardly positioned, as is sometimes necessary in economy aircraft seating, for example. Thus it is preferred if the engagement of the arresting mechanism is prevented from taking place as a final portion of the cable length is rewound.
For example, engagement of the arresting mechanism may be prevented as the rewind bias torque reaches a particular magnitude. Alternatively, the cable may carry a physical marker such as a mechanical stop, or a marker having different optical, electrical resistance, magnetic or other properties to the remainder of the cable. This marker can then be sensed by the arresting mechanism to disable or enable its engagement capability.
Preferably however, the engagement capability of the arresting mechanism is enabled or disabled after a predetermined degree of rotation of the spool. For example, the arresting mechanism may comprise a ratchet and pawl, the pawl being mechanically connected to the spool in a manner that prevents it from co-operating with the ratchet over a predetermined degree of rotation of the spool. The mechanical connection may comprise a gear train and/or a cam surface arranged to move the pawl into or out of co-operation with the ratchet.
The invention and various preferred objects, features and advantages thereof will be further understood from the following description of illustrative embodiments made with reference to the accompanying drawings.